Help me: Why won’t my newly assembled PC start?

There are plenty of reasons why a newly PC won’t start. Resolving an issue is usually fairly simple, the problem lies in finding it, which usually involves testing different possibilities.

Here’s what to look for to find the main problems:(Note this is not an extensive list of all the problems/solutions, but rather a simple quick guide for the most common issues)

If the PC doesn’t power on at first:
This is most probably due to you forgetting to plug in a power cable/cord.

Is the power cord plugged into a wall outlet and into the power supply?

Is the power supply switched on?

Is the power lead cable (power SW) from the case plugged into the motherboard?

Make sure that all the power cables are plugged in. The video card may require one or two PCI-Express power connectors and the motherboard requires the 24-pin ATX connector along with the 4/8-pin ATX power.

If the PC still doesn’t power on after that:This might be due to a broken power SW switch (Try using the reset one instead to see if that one does work.)
If the PC still doesn’t on even while trying the reset switch instead, the problem is most likely due to a defective power supply. Try an ATX Power Supply Tester ($10)

If the PC doesn’t boot (Power up, but nothing is displayed on the monitor):

Once again, make sure that all the power cables are plugged in. The video card may require one or two PCI-Express power connectors and the motherboard requires the 24-pin ATX connector along with the 4/8-pin ATX power. Other components such as hard drives and optical drives also require dedicated power.

Make sure that memory modules are plugged where they should be, that is slot 1 and 3 (some motherboards work only with slot 2 and 4). Try one stick a time. Make sure that they are fully seated.

Double-check your video card to make sure that it is fully inserted.

Ensure that the motherboard stand-offs are installed correctly (including the insulation washers) and that the motherboard is not touching any part of the case.

Check your CPU for proper seating, and possibly a bent pin on the CPU or motherboard.

Think through everything you have done in the setup, even the heat sink and thermal paste.

If you have a speaker for the mother/case, listen to the beep code and find out the problem with your manual. You didn’t get a speaker with your case? Use this kit from FrozenCPU ($10)

If the PC still won’t boot:
1- Clear the CMOS: This can be done either with the jumper (located close to the battery on the motherboard) or by removing the battery.

2-Remove one component at a time, until the PC boot. The last component that was removed before it booted is most likely the problem. Try using an alternative part if possible, otherwise consider a return (RMA).

3- I recommend that you do your build outside of the case at first, so if you have a problem, it’s easier to troubleshoot. I would take the motherboard out of the case and just set it on the foam pad that came with the box that the motherboard came in. You can also set the pad on the actual box. You should not have to take the PSU out of the case, just set the case near the board.

Hook up the following:

24-pin main ATX power

8-pin 12v CPU power

CPU cooler fan

1 stick of RAM in the first slot

video card

6-pin/8-pin PCIe video card power connector(s)

monitor

mouse

keyboard

2-pin f_panel POWER SW connector

The power sw comes from the case power switch and the proper connector should be labeled. The motherboard manual will say where it goes, and there should be something like “PSW” or “Power SW” printed on the board with a color code for the proper header.

Plug in the PSU, turn on the power switch, and push the power button. You may have to hold the power button down for a few seconds.

If that works, add one part back in at the time, while booting the PC every time. If it stops booting, it is most likely due to the last part that you inserted.

Conclusion

If you still have problems with your PC not powering or not booting after using this guide, leave a post describing your problem and everything that you’ve tried on the forums and we’ll do my best to help you out.

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About The Author

HR Founder - Computer expert with over 16 years of experience in building, fixing and modifying PCs.
Over the years, I’ve developed a passion for PC hardware and now I enjoy helping others build their own PCs!
In April 2008, I launched Hardware Revolution and ... Read more at my about page

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